DEVELOPMENT OF THE ANTHROPOMORPHIC ROBOT WITH CARBON-FIBER EPOXY COMPOSITE-MATERIALS

Abstract

The material for the robot structure should have high specific stiffness (stiffness/density) to give positional accuracy and fast maneuverability to the robot. Also, the high material damping is beneficial because it can dissipate the structural vibration induced in the robot structure. This cannot be achieved through conventional materials such as steel and aluminum because these two materials have almost the same specific stiffnesses which are not high enough for the robot structure. Moreover, steel and aluminum have low material dampings. Composites which usually consist of very high specific modulus fibers and high damping matrices have both high specific stiffnesses and high material dampings. Therefore, in this work, the forearm of an anthropomorphic robot which has 6 degrees of freedom, 70 N payload and 0.1 mm positional accuracy of the end effector was designed and manufactured with high modulus carbon fiber epoxy composite because the magnitudes of the mass and moment of inertia of the forearm of an anthropomorphic robot are most important due to its farthest position from the robot base. Two power transmission shafts which deliver the power of the motors positioned at the rear of the robot forearm to the wrist and the end effector were also designed and manufactured with high modulus carbon fiber epoxy composite to reduce weight and rotational inertia. The mass reduction of the manufactured composite forearm was 15.9 kg less than the steel forearm. The natural frequencies and damping capacity of the manufactured composite arm were measured by the fast Fourier transform method and compared to those for the steel arm. From the test, it was found that both the fundamental natural frequency and damping ratio of the composite arm of the robot were much higher than those of the steel arm.